Method and apparatus for reducing acoustic feedback from a speaker to a microphone in a communication device

ABSTRACT

A method and apparatus to reduce acoustic feedback from a speaker to a microphone in a communication device. An audio signal can be reproduced by an apparatus. An audible signal of at least one near-end user can be voice activity detected at the apparatus. At least one audio output channel of multiple audio output channels can be operated on to attenuate acoustic pressure representative of the audio signal near at least one microphone aperture location when the audible signal of the at least one near-end user is detected at the apparatus.

BACKGROUND

1. Field

The present disclosure is directed to a method and apparatus forreducing acoustic feedback from a speaker to a microphone in acommunication device.

2. Introduction

Presently, traditional speakerphones have one speaker and one microphonelocated a distance from the speaker. Portable communication devices,such as cellular phones, smartphones, tablet computers, and othercommunication devices also have speakerphone functionality. When aspeakerphone mode is operational, the microphone on the device picks upa local user's voice for transmission to a remote user. Unfortunately,the microphone also picks up a remote user's voice coming through thespeaker and sends it back to the remote user, which results in theremote user hearing an undesirable echo to what they are saying. Toavoid the echo, speakerphones employ echo cancellation that processesthe signal after it is received at the microphone to remove the echo.However, the echo cancellation is not optimal, especially when there ismore than one operational speaker on the speakerphone.

Thus, there is a need for a method and apparatus for reducing acousticfeedback from a speaker to a microphone in a communication device.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of thedisclosure can be obtained, a description of the disclosure is renderedby reference to specific embodiments thereof which are illustrated inthe appended drawings. These drawings depict only example embodiments ofthe disclosure and are not therefore to be considered to be limiting ofits scope.

FIG. 1 is an example schematic diagram of a system according to apossible embodiment;

FIG. 2 is an example flowchart illustrating the operation of anapparatus according to a possible embodiment; and

FIG. 3 is an example block diagram of an apparatus according to apossible embodiment.

DETAILED DESCRIPTION

Embodiments provide a method and apparatus for reducing acousticfeedback from a speaker to a microphone in a communication device.According to a possible embodiment, an audio signal can be reproduced byan apparatus. An audible signal of at least one near-end user can bevoice activity detected at the apparatus. At least one audio outputchannel of multiple audio output channels can be operated on toattenuate acoustic pressure representative of the audio signal near atleast one microphone aperture location when the audible signal of the atleast one near-end user is detected at the apparatus.

For example, when a near-end user is speaking while audio is playingthrough a speaker of a device, they are paying less attention to theaudio being reproduced than to what they are saying. Thus, when the useris talking, the quality of the audio playback can be compromised withlittle effect on the audio quality perceived by the user. While somecommunication devices have one speaker, others have stereo or even morespeakers. Using stereo or multiple speakers when reproducing audio onthese devices provides more output. However, because the stereo speakersare located a distance from each other on the device, one of the stereospeakers may be closer to the microphone than the other speaker.Otherwise, the microphone can be placed further away from a singlespeaker. This causes a problem because it increases the audio signalspicked up at the microphone from the closer speaker and causes increasedecho. This is also a problem when other sources of audio are playingthrough the speakers, which can be picked up by the microphone that iscloser to the closest speaker. Embodiments can improve microphonereception of an audio signal of a user while reducing microphonereception of audio signals playing through speakers of an apparatus.

FIG. 1 is an example schematic diagram of a system 100 according to apossible embodiment. The system 100 can include a communication device110, a user 120, and a network 130. The communication device 110 caninclude multiple audio channels that are represented in the system 100as speakers with apertures 122 and 124. The communication device 110 canalso include at least one microphone with an aperture 126, and canoptionally include at least one other microphone with an aperture 128.The communication device 110 can be any device that can receive audiblesignals 150 from the user 120 and reproduce audio signals 140 receivedremote from the communication device 110 and/or stored locally on thecommunication device 110. The communication device 110 can be a wirelessterminal, a portable wireless communication device, a smartphone, acellular telephone, a flip phone, a personal digital assistant, a laptopcomputer, a personal computer, a selective call receiver, a tabletcomputer, a speakerphone, or any other device that is capable ofreceiving audible signals 150 from the user 120 and reproducing audiosignals 140. The communication device 110 can send and receive the audiosignals over the network 130 and can also reproduce the audio signal 140from data stored on the device. Furthermore, the communication device110 can voice activity detect an audible signal 150 of at least onenear-end user 120.

The network 130 can include any type of network that is capable ofsending and receiving network communication signals. For example, thenetwork 130 can include a wired communication network, a wirelesscommunication network, a cellular telephone network, a Time DivisionMultiple Access (TDMA)-based network, a Code Division Multiple Access(CDMA)-based network, an Orthogonal Frequency Division Multiple Access(OFDMA)-based network, a Long Term Evolution (LTE) network, a 3rdGeneration Partnership Project (3GPP)-based network, a satellitecommunications network, a high altitude platform network, and/or othercommunication networks.

FIG. 2 is an example flowchart 200 illustrating the operation of anapparatus, such as the communication device 110, according to a possibleembodiment. At 210, the flowchart 200 can begin.

At 220, an audio signal can be reproduced. Audio sources of thereproduced audio signal can include locally memory stored audio,streamed audio, synthesized audio, voice call audio, such as from afar-end user, multimedia audio, music, audio alerts, ring-tones, andother sources of audio. According to a possible embodiment, the audiosignal can be received in a downlink signal from a far-end user over awireless or wired network.

At 230, a determination can be made as to whether an audible signal ofat least one near-end user has been voice activity detected at theapparatus. While voice activity detection is used to detect the audiblesignal, the audible signal may or may not be a voice signal. Inparticular, the audible signal can be an audible signal intentionallygenerated by a user, such as a voice signal, or can be anotherintentional audible signal generated by the near-end user and theintentional audible signal can be voice activity detected even if it isnot a voice signal. For example, the intentional audible signal can bespeech of the near-end user during a voice call, can be a command fromthe near-end user to activate a voice assistant on an electronic device,and/or can be a sound intentionally generated by a user. Furtherexamples of the intentional audible signal can include sounds from auser's mouth, such as clucking or clicking, sounds from a user's hands,such as tapping, snapping, and clapping, sounds from other sources, suchas an alarm, a buzzer, or music, and/or any other sound a user cangenerate. The apparatus can determine the audible signal is intentionalby comparing the captured sound to known sounds in its memory, byperforming speaker identification and recognizing the voice of the ownerof the device or one of a number of registered users, by processing thesound with a voice activity detection algorithm, or by any other processof determining a type of sound. The user can generate or set up theintentional audible signal to trigger an activity or process on theapparatus. According to a possible embodiment, the audio signal can be adownlink signal containing speech audio from the far-end user and theaudible signal of at least one near-end user can be an audible speechsignal of the at least one near-end user.

The voice activity detection can include any known and future voiceactivity detection including, a single microphone/channel voice activitydetector, a multi-microphone/multi-channel voice activity detector, anoptical voice activity detector, a laser based voice activity detector,a vibration based voice activity detector, a radio frequency voiceactivity detector, and any other device or process that detects anaudible signal. If the audible signal has not been determined to bevoice activity resulting in a negative voice activity detection, thenthe audio signal can continue to be reproduced at 220.

At 240, when the audible signal of the at least one near-end user isdetected at the apparatus at 230, at least one audio output channel ofmultiple audio output channels can be operated on to attenuate acousticpressure representative of the audio signal near at least one microphoneaperture location. A microphone aperture can be an opening in a housingthat feeds acoustic pressure to the microphone. An audio output channelcan include a chain of one or more of a processor, a mixer, a Digital toAnalog (D/A) converter, an audio amplifier, and/or an output transducerand its associated aperture, and/or any other process, device, orcircuit that can reproduce an audio signal. An output transducer can bea speaker, a linear vibrator, a piezoelectric transducer, and/or anyother transducer that can generate sound.

According to a possible embodiment, the multiple audio output channelscan include at least one speaker each to provide a plurality ofspeakers. The one audio output channel of multiple audio output channelscan be operated on by attenuating the audio output channel containing aspeaker that is the loudest at the microphone aperture location. Theloudest speaker can be the closest speaker to the microphone aperturelocation or can be another speaker that is the loudest at the microphoneaperture location. Attenuating can be performed by ramping attenuationfrom a full playback level to a desired attenuation level, therebygradually reducing the perceived volume from the loudest speaker. Thedesired level of attenuation can even mean completely muting the loudestspeaker.

According to another possible embodiment, the microphone can include atleast one microphone, or two or more microphones, with correspondingapertures, each microphone and aperture at a different location in thehousing. The one audio output channel of multiple audio output channelscan be operated on by filtering a signal to at least one speaker tocreate destructive interference of the reproduced audio signal at themicrophone aperture location of the at least one microphone. The oneaudio output channel of multiple audio output channels can also beoperated on by phasing a signal to at least one speaker to createdestructive interference of the reproduced audio signal at eachmicrophone aperture location of the at least one microphone. Forexample, a reduction of signal at one or more microphone location can beachieved by appropriately phasing the signal to one or both of thespeakers, such that there is destructive interference at each microphonelocation. The phasing can be frequency dependent to allow for maximalcancellation at each frequency for each specified location. In thisembodiment the signal prior to the phase filter can be monophonic. Ifthe downlink signal is stereo, when the voice activity detection istrue, the stereo signal can be summed to monophonic, and then theappropriate filter or filters can be applied. A cancellation filter canbe applied to one channel while no filter is applied to the other, or aphase delay can be split between complimentary filters on each channel.The complementary filters may or may not be symmetric depending on theposition and number of microphones that require cancellation.

According to another possible embodiment, the audio signal can be astereo signal. The one audio output channel of multiple audio outputchannels can then be operated on by applying a cross-talk canceller witha minimum at a microphone aperture location of the at least onemicrophone to reduce the level of the reproduced audio signal at themicrophone location. For example, when the downlink signal is stereo,the reduction of the signal at the microphone location can be achievedby implementing a stereo cross-talk canceller with a minimum at themicrophone location. The cross-talk canceller can be applied when thevoice activity detection is true, and removed when the voice activitydetection is false. The gain of the cross-talk cancellation may beramped from no attenuation to full attenuation over a period of timeafter the voice activity detection is detected true. The canceller gaincan then be ramped back to no attenuation after a false voice activityis detected.

In another embodiment, when there is more than one microphone and thephysical signal produced by one or combination of multiple speakers at afirst microphone aperture is attenuated, minimized, and/or cancelled,such as through the application of cross-talk canceller, or filtering,or phasing, or attenuation, or by other method, the other microphone(s)can be reduced, such as muted or otherwise attenuated, and/or have theirsignals replaced by a signal produced by the microphone that is coupledto the first microphone aperture. For example, the apparatus can includea first microphone acoustically coupled to the at least one microphoneaperture location and a second microphone, and the output of the secondmicrophone can be reduced when the audible signal of the at least onenear-end user is detected at the apparatus.

According to another possible embodiment, the at least one audio outputchannel can include a plurality of audio output channels and the audiosignal can be a multiple channel signal. For example, a multiple channelsignal can be a stereo signal, a quadraphonic signal, a surround soundsignal, or any other multiple channel signal. The one audio outputchannel of multiple audio output channels can then be operated on byconverting the multiple channel signal to a monaural signal and feedingthe monaural signal to at least two of the plurality audio outputchannels. The monaural signal can also be fed to more or all of theplurality audio output channels. In this embodiment, when the audiosignal is stereo or more channels, the stereo or more channel signal canbe converted to a monaural signal when the voice activity detection istrue. In this case, the conversion to monaural can be done without phasecancellation, but optionally with attenuation of the speakers. This canallow the use of a monaural echo-canceller instead of requiring a stereoecho canceller. The stereo signal can also be converted to a monauralsignal to aid in echo cancellation of the microphone signal(s) that feedthe voice activity detection.

For example, embodiments can use an uplink Voice Activity Detector (VAD)decision to attenuate the speaker of the at least one audio outputchannel when the local user is talking. The speaker being attenuated canbe the one loudest at the microphone. The attenuation can be any levelfrom a full mute up to a level that is able to be cancelled by the echocanceller in the device. For improved user experience, the gain on thespeaker nearest the microphone can be ramped at a given rate from thefull level playback to the desired attenuation level, such as using areduction of level of 6 dB/second, or any other reduction rate. The gaincan ramp back up to full volume after a false VAD is detected. At 250,the flowchart 200 can end.

It should be understood that, notwithstanding the particular steps asshown in the figures, a variety of additional or different steps can beperformed depending upon the embodiment, and one or more of theparticular steps and embodiments can be rearranged, combined, repeatedand/or eliminated entirely depending upon the embodiment. Also, some ofthe steps performed can be repeated on an ongoing or continuous basissimultaneously while other steps are performed. Furthermore, differentsteps can be performed by different elements or in a single element ofthe disclosed embodiments.

FIG. 3 is an example block diagram of an apparatus 300, such as thecommunication device 110, according to a possible embodiment. Theapparatus 300 can include a housing 310, a controller 320 within thehousing 310, at least one microphone 322 coupled to the controller 320and corresponding aperture 323, a display 324 coupled to the controller320, a transceiver 326 coupled to the controller 320, an antenna 328coupled to the transceiver 326, a user interface 330 coupled to thecontroller 320, a memory 332 coupled to the controller 320, a networkinterface 334 coupled to the controller 320, and a voice activitydetection module 336. The apparatus 300 can also include at least twoaudio output channels 340 and 350. Each audio output channel can includea mixer 341 and 351, a Digital to Analog (D/A) converter 342 and 352, anamplifier 343 and 353, a transducer 344 and 354, an aperture 345 and355, and/or any other useful device or circuit for reproducing an audiosignal. The apparatus 300 can perform the methods described in all theembodiments.

The display 324 can be a viewfinder, a liquid crystal display (LCD), alight emitting diode (LED) display, a plasma display, a projectiondisplay, a touch screen, or any other device that displays information.The transceiver 326 can include a transmitter and/or a receiver. Themicrophone 322 can include a microphone, a speaker, a transducer, or anyother audio input circuitry. The microphone 322 can be acousticallycoupled to the microphone aperture 323 to receive acoustic signals. Theuser interface 330 can include a keypad, a keyboard, buttons, a touchpad, a joystick, a touch screen display, another additional display, orany other device useful for providing an interface between a user and anelectronic device. The network interface 334 can be a universal serialbus port, an Ethernet port, an infrared transmitter/receiver, a USBport, an IEEE 1393 port, a WLAN transceiver, or any other interface thatcan connect an apparatus to a network or computer and that can transmitand receive data communication signals. The memory 332 can include arandom access memory, a read only memory, an optical memory, a flashmemory, a removable memory, a hard drive, a cache, or any other memorythat can be coupled to a wireless communication device.

The apparatus 300 and/or the controller 320 may implement any operatingsystem, such as Microsoft Windows®, UNIX®, or LINUX®, Android™, or anyother operating system. Apparatus operation software may be written inany programming language, such as C, C++, Java or Visual Basic, forexample. Apparatus software may also run on an application framework,such as, for example, a Java® framework, a .NET® framework, or any otherapplication framework. The software and/or the operating system may bestored in the memory 332 or elsewhere on the apparatus 300. Theapparatus 300 and/or the controller 320 may also use hardware toimplement disclosed operations. For example, the controller 320 may beany programmable processor. Disclosed embodiments may also beimplemented on a general-purpose or a special purpose computer, aprogrammed microprocessor or microprocessor, peripheral integratedcircuit elements, an application-specific integrated circuit or otherintegrated circuits, hardware/electronic logic circuits, such as adiscrete element circuit, a programmable logic device, such as aprogrammable logic array, field programmable gate-array, or the like. Ingeneral, the controller 320 may be any controller or processor device ordevices capable of operating an electronic device and implementing thedisclosed embodiments. The voice activity detection module 336 can be ahardware module, can be a software module, can be part of the controller320, can be separate from the controller 320, can be stored in thememory 332, can be implemented by the controller 320 or by some otherprocessor, can reside within apparatus 300, can exist in a cloud basedprocessor, and/or can be any other hardware or software module that candetect an audible signal of at least one near-end user at the apparatus300.

In operation, the audio output channels 340 and 350 can reproduce anaudio signal. The voice activity detecting module 336 can detect anaudible signal of at least one near-end user at the apparatus 300.

The controller 320 can operate on at least one audio output channel 340of the plurality of audio output channels 340 and 350 to attenuateacoustic pressure representative of the audio signal near the at leastone microphone aperture 323 location when the audible signal of the atleast one near-end user is detected at the apparatus 300. According to apossible embodiment, the controller 320 can operate on the at least oneaudio output channel 340 by attenuating the audio output channel 340containing a loudest speaker, such as the transducer 344, at themicrophone aperture 323. Attenuating can include ramping attenuationfrom a full playback level to a desired attenuation level, therebygradually reducing the perceived volume from the loudest speaker.

According to a possible embodiment, the controller 320 can operate onthe at least one audio output channel 340 by filtering a signal to atleast one speaker to create destructive interference of the reproducedaudio signal at the microphone aperture 323. The controller 320 can alsooperate on the at least one audio output channel 340 by phasing a signalto at least one speaker to create destructive interference of thereproduced audio signal at the microphone aperture 323. The controller320 can additionally create destructive interference at more than onemicrophone aperture. The controller 320 can further reduce an output ofat least one second microphone of the at least one microphone 322 whenthe audible signal of the at least one near-end user is detected at theapparatus 300.

According to a possible embodiment, the audio signal can be a stereosignal. The controller 320 can operate on the at least one audio outputchannel 340 by applying a cross-talk canceller with a minimum at themicrophone aperture location 323 of the at least one microphone 322 toreduce the level of the reproduced audio signal at the microphoneaperture 323 location. According to a related implementation, the audiosignal can be a multiple channel signal and the controller 320 canconvert the multiple channel signal to a monaural signal and feed themonaural signal to at least two of the plurality audio output channels340 and 350.

The method of this disclosure can be implemented on a programmedprocessor. However, the controllers, flowcharts, and modules may also beimplemented on a general purpose or special purpose computer, aprogrammed microprocessor or microcontroller and peripheral integratedcircuit elements, an integrated circuit, a hardware electronic or logiccircuit such as a discrete element circuit, a programmable logic device,or the like. In general, any device on which resides a finite statemachine capable of implementing the flowcharts shown in the figures maybe used to implement the processor functions of this disclosure.

While this disclosure has been described with specific embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. For example,various components of the embodiments may be interchanged, added, orsubstituted in the other embodiments. Also, all of the elements of eachfigure are not necessary for operation of the disclosed embodiments. Forexample, one of ordinary skill in the art of the disclosed embodimentswould be enabled to make and use the teachings of the disclosure bysimply employing the elements of the independent claims. Accordingly,embodiments of the disclosure as set forth herein are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure.

In this document, relational terms such as “first,” “second,” and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The phrase“at least one of” followed by a list is defined to mean one, some, orall, but not necessarily all of, the elements in the list. The terms“comprises,” “comprising,” or any other variation thereof, are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. An elementproceeded by “a,” “an,” or the like does not, without more constraints,preclude the existence of additional identical elements in the process,method, article, or apparatus that comprises the element. Also, the term“another” is defined as at least a second or more. The terms“including,” “having,” and the like, as used herein, are defined as“comprising.” Furthermore, the background section is written as theinventor's own understanding of the context of some embodiments at thetime of filing and includes the inventor's own recognition of anyproblems with existing technologies and/or problems experienced in theinventor's own work.

We claim:
 1. A method comprising: reproducing an audio signal by anapparatus; voice activity detecting an audible signal of at least onenear-end user at the apparatus; and operating on at least one audiooutput channel of multiple audio output channels to attenuate acousticpressure representative of the audio signal near at least one microphoneaperture location when the audible signal of the at least one near-enduser is detected at the apparatus.
 2. The method according to claim 1,wherein the multiple audio output channels comprise a plurality ofspeakers, and wherein operating comprises attenuating the audio outputchannel containing a speaker that is loudest at the microphone aperturelocation.
 3. The method according to claim 2, wherein attenuatingincludes ramping attenuation from a full playback level to a desiredattenuation level, thereby gradually reducing the perceived volume fromthe loudest speaker.
 4. The method according to claim 1, whereinoperating comprises filtering a signal to at least one speaker to createdestructive interference of the reproduced audio signal at the at leastone microphone aperture location.
 5. The method according to claim 1,wherein operating comprises phasing a signal to at least one speaker tocreate destructive interference of the reproduced audio signal at the atleast one microphone aperture location.
 6. The method according to claim1, wherein the audio signal comprise a stereo signal, and whereinoperating comprises applying a cross-talk canceller with a minimum at amicrophone aperture location of the at least one microphone to reducethe level of the reproduced audio signal at the microphone location. 7.The method according to claim 1, wherein the at least one audio outputchannel comprises a plurality of audio output channels, wherein theaudio signal comprises a multiple channel signal, and wherein operatingcomprises converting the multiple channel signal to a monaural signaland feeding the monaural signal to at least two of the plurality audiooutput channels.
 8. The method according to claim 1, wherein the audiosignal comprises a downlink signal containing speech audio from thefar-end user, and wherein audible signal of at least one near-end usercomprise an audible speech signal of the at least one near-end user. 9.The method according to claim 1, wherein the apparatus comprises acellular phone.
 10. The method according to claim 1, wherein theapparatus includes a first microphone acoustically coupled to the atleast one microphone aperture location and the apparatus includes asecond microphone, wherein the method further comprises reducing anoutput of the second microphone when the audible signal of the at leastone near-end user is detected at the apparatus.
 11. The method accordingto claim 1, wherein the apparatus includes a first microphoneacoustically coupled to the at least one microphone aperture locationand the apparatus includes a second microphone, wherein the methodfurther comprises substituting a signal from the second microphone witha signal from the first microphone when the audible signal of the atleast one near-end user is detected at the apparatus.
 12. An apparatuscomprising: a housing; at least one microphone aperture at a location inthe housing; at least one microphone acoustically coupled to the atleast one microphone aperture; a plurality of audio output channelsconfigured to reproduce an audio signal; a voice activity detectingmodule configured to detect an audible signal of at least one near-enduser at the apparatus; and a controller coupled to the microphone, theplurality of audio output channels, and the voice activity detectingmodule, the controller configured to operate on at least one audiooutput channel of the plurality of audio output channels to attenuateacoustic pressure representative of the audio signal near the at leastone microphone aperture location when the audible signal of the at leastone near-end user is detected at the apparatus.
 13. The apparatusaccording to claim 12, wherein the plurality of audio output channelseach comprise at least one speaker, and wherein the controller isconfigured to operate on the at least one audio output channel byattenuating the audio output channel containing a speaker that isloudest at the microphone aperture location.
 14. The apparatus accordingto claim 13, wherein attenuating includes ramping attenuation from afull playback level to a desired attenuation level, thereby graduallyreducing the perceived volume from the loudest speaker.
 15. Theapparatus according to claim 12, wherein the controller is configured tooperate on the at least one audio output channel by filtering a signalto at least one speaker to create destructive interference of thereproduced audio signal at the at least one microphone aperturelocation.
 16. The apparatus according to claim 12, wherein thecontroller is configured to operate on the at least one audio outputchannel by phasing a signal to at least one speaker to createdestructive interference of the reproduced audio signal at the at leastone microphone aperture location.
 17. The apparatus according to claim12, wherein the audio signal comprise a stereo signal, and wherein thecontroller is configured to operate on the at least one audio outputchannel by applying a cross-talk canceller with a minimum at themicrophone aperture location of the at least one microphone to reducethe level of the reproduced audio signal at the microphone aperturelocation.
 18. The apparatus according to claim 12, wherein the audiosignal comprises a multiple channel signal, and wherein the controlleris configured to convert the multiple channel signal to a monauralsignal and feed the monaural signal to at least two of the pluralityaudio output channels.
 19. The apparatus according to claim 12, whereinthe audio signal comprises a downlink signal containing speech audiofrom the far-end user, and wherein audible signal of at least onenear-end user comprise an audible speech signal of the at least onenear-end user.
 20. The apparatus according to claim 12, wherein theapparatus comprises a cellular phone.
 21. The apparatus according toclaim 12, wherein the at least one microphone comprises a firstmicrophone, wherein the apparatus further comprises at least one secondmicrophone, wherein the controller is configured to reduce an output ofthe at least one second microphone when the audible signal of the atleast one near-end user is detected at the apparatus.
 22. A methodcomprising: receiving, at a cellular device, a downlink signalcontaining an audio signal from a far-end user; reproducing the audiosignal by the cellular device; voice activity detecting an audiblespeech signal of at least one near-end user at a microphone at thecellular device; and operating on at least one audio output channel ofmultiple audio output channels to attenuate acoustic pressurerepresentative of the audio signal near a microphone aperture locationfor the microphone when the audible speech signal of the at least onenear-end user is detected at the cellular device.
 23. The methodaccording to claim 22, wherein the cellular device comprises a pluralityof speakers, and wherein operating comprises attenuating the audiooutput channel containing a closest speaker of the plurality of speakersto the microphone aperture location.